1. Field of the Invention
The present invention relates to a fuel-cell system.
2. Description of the Related Art
For example, Japanese Patent Laid-open No. 2007-165186 discloses a fuel-cell system in which a period (called a driving interval) as a sum of a valve-open duration and a valve-closed duration of an injector can be changed to be lengthened or shortened according to the load on the fuel cell.
Generally, in the fuel-cell systems, in some cases, a rapid change in the load or opening of a purge valve can cause a variation in the anode pressure during a driving interval of the injector. In addition, in the conventional fuel-cell systems, it is necessary to wait for the next driving interval before opening a purge valve for controlling the anode pressure. Therefore, in the conventional fuel-cell systems, it is impossible to quickly control the anode pressure even when the anode pressure rapidly varies, so that stoichiometric insufficiency can occur in the fuel cell.
In view of above, the object of the present invention is to provide a fuel-cell system which is excellent in pressure controllability, and can quickly control the anode pressure even when the anode pressure rapidly varies.